TIME-VARYING RECONNECTION - IMPLICATIONS FOR MAGNETOPAUSE OBSERVATIONS

We discuss the implications of results arising from an analysis of a P etschek-type reconnection model for the interpretation of data obtaine d at the terrestrial magnetopause. In this model, reconnection is init iated through the. introduction of a reconnection electric field in th e diffusion region. The. magnitude of the electric, field is considere d to be small compared to the product of characteristic values of the magnetic, field strength and Alfven speed in the system; that is, we s tudy the case of weak reconnection only. Outside the. diffusion region , the behavior of the plasma is governed by the ideal MHD equations. P etschek's original analysis is generalized through the: introduction o f a spatially and temporally varying reconnection rate., that is, the reconnection line has a finite length and the! reconnection electric f ield along it val ies in time Additionally, the magnetic. fields on ei ther side of the current sheet (although uniform initially) may have a rbitrary strength and are, skewed relative to each other. New features are that (1) the plasma velocity may have a shear across the current layer, and (2) the. densities on either side of the! current sheet may be. different in general. The reconnection electric field initiates a localized disruption of tile current sheet and the associated disturb ances are propagated into the system by MHD waves. With this model we are able to explain and interpret various features ol,served at the te rrestrial magnetopause, such as accelerated plasma flows and flux tran sfer events. We describe magnetic field signatures predicted by our mo del. We also show that reconnection is capable of generating surface w aves. A property of our model is that it predicts a displacement of th e magnetopause when time-dependent reconnection is occurring.